When used, hair strand tests should form only part of the evidential picture. They should not be used in isolation to reach evidential conclusions: “You cannot put everything on the hair strand test.”

The results of hair strand tests should only be used to determine whether or not there has been excessive alcohol consumption by the use of the cut off level.

A level lower than the cut off level is consistent with abstinence or social drinking. There is no agreed cut off level for the line between abstinence and social drinking.

“The tests are not designed to establish abstinence or social drinking” (paragraph 22(iii)).

Research evidence suggests that 10% of the results obtained by hair strand testing are false positives.

Hair strand testing is therefore valuable to form part of an evidential picture when the aim of the testing is to determine whether a person has been consuming more than 7 units of alcohol a day, on average, over the testing period. However, it is only valuable when used in conjunction with other evidence such as other forms of testing and other forensic evidence.